Aircraft typically carry cargo on pallets or in large containers called unit load devices (ULDs). ULDs and pallets are available in several different standardized lengths and widths. During flight, all ULDs and/or pallets must be securely retained to prevent damage to the aircraft and/or to the cargo and to maintain aircraft stability and balance. Accordingly, cargo restraints are used to restrain the ULDs and/or pallets in their stowed positions within an aircraft's cargo compartment. Such cargo restraints are typically mounted to an aircraft's cargo deck at fixed points that correspond to lower edges of the stowed ULD and/or pallet.
In some aircraft, deflection of the aircraft's wings during flight can cause temporary changes to the aircraft's cargo deck, particularly in the area of the aircraft's wing box. For example, typical flight loads cause upward deflection of the aircraft's wing tips, compressing the entire upper wing surface, which can affect the cargo deck, moving the left and right hand cargo restraints closer together. Because cargo restraints are designed as fixed structures that offer no flex, such lateral compression of the aircraft's cargo deck can cause stowed ULDs and/or pallets to be squeezed between their cargo restraints and can result in substantial loads on the cargo restraints and the structure of the aircraft. In extreme cases, such loads on the cargo restraints may overload the aircraft's support structure.
Attempts have been made to design cargo restraints to attenuate the damaging loads transmitted to the aircraft's support structure resulting from fixed cargo restraints squeezing the stowed ULDs and/or pallets due to deflection of the aircraft's wings. However, such attempts add undesirable complexity and cost to the cargo restraints.
Accordingly, those skilled in the art continue with research and development efforts in the field of aircraft cargo restraints.